Equilibrium and kinetic studies of chromium adsorption from wastewater by functionalized multi-wall carbon nanotubes

The equilibrium and kinetics of hexavalent chromium adsorption on multi-wall carbon nanotube (MWCNT) functionalized with ethylenediaminetetraacetic acid (EDTA) and sulfuric acid have been studied. Adsorption kinetics was evaluated using pseudo-first order, pseudo-second order, and intraparticle diffusion models. Langmuir, Freundlich, and Temkin isotherms were used to analyze the equilibrium. The studies were carried out by considering the effects of the main operating parameters, such as contact time (0-250 min), adsorbent dosage (20-60 mg), and pH (3-9). Under the optimum conditions, the contact time, functionalized multi-wall carbon nanotube (f-MWCNT) dosage and pH were 150, 60 mg and 3. The Langmuir isotherm fits the experimental data (R-2 = 0.996) significantly better than the other isotherms. Kinetic studies showed that the adsorption followed a pseudo-second order reaction. The maximum adsorption efficiency was about 99.8 %. These results showed that f-MWCNT can be used as an efficient adsorbent for chromium removal.